An ultrasonic diagnostic apparatus is a diagnostic apparatus that displays an image of in vivo information, and is used for noninvasive real-time observation as an inexpensive apparatus without exposure, as compared to other image diagnostic apparatuses such as an X-ray diagnostic apparatus and an X-ray computed tomography apparatus. The ultrasonic diagnostic apparatus has a wide scope and field of application and is applied to diagnosis of a circulatory organ such as a heart, an abdominal organ such as a liver or a kidney, a peripheral blood vessel, obstetrics and gynecology, a breast cancer, and the like.
In general, the ultrasonic diagnostic apparatus transmits an ultrasonic wave into a subject using an ultrasonic probe, and receives a reflected wave from the subject, thereby obtaining diagnostic information (ultrasonic image) in the subject. Examples of the operation modes of the ultrasonic diagnostic apparatus are a B mode (B) to display a two-dimensional morphological image (B-mode image), a color mode (C) to display a two-dimensional blood flow image (color Doppler mode image), and a Doppler mode (D) to display a Doppler waveform (Doppler spectrum image).
One of the modes to display images in a plurality of operation modes in such an ultrasonic diagnostic apparatus is the Triplex mode. According to the Triplex mode, images in, for example, the B mode, the color mode, and the Doppler mode can be displayed simultaneously. Note that in the Triplex mode, two types of scan including interleave scan and segment scan are used.
The interleave scan is a scan method of alternately transmitting ultrasonic waves (beams) corresponding to the B mode, the color mode, and the Doppler mode. In the interleave scan, the quality of an image in the Doppler mode (to be simply referred to as the image quality of the Doppler mode hereinafter) is high, as compared to the segment scan. However, a constraint is placed on the upper limit of the velocity of the blood flow.
On the other hand, the segment scan is a scan method of transmitting an ultrasonic wave corresponding to the Doppler mode continuously for a predetermined period and then transmitting ultrasonic waves corresponding to the B mode and the color mode. Note that according to the segment scan, a Doppler waveform is generated by interpolation when transmitting the ultrasonic waves corresponding to the B mode and the color mode. In the segment scan, the upper limit of the velocity of the blood flow can be set higher than in the above-described interleave scan. However, the image quality of the Doppler mode degrades because the Doppler waveform in the Doppler mode is estimated by interpolation.
To improve the image quality of the Doppler mode in the above-described segment scan, the period (gap period) in which the ultrasonic wave corresponding to the Doppler mode is not transmitted needs to be shorter. In other words, the number of data of the Doppler mode (that is, the transmission count of the ultrasonic wave corresponding to the Doppler mode) is increased. In this case, however, since the number of data of the B mode and the color mode (that is, the transmission count of the ultrasonic waves corresponding to the B mode and the color mode) decreases, the qualities of the images in the B mode and the color mode (to be simply referred to as the image qualities of the B mode and the color mode hereinafter) degrade. For this reason, data distribution to the B mode, the color mode, and the Doppler mode needs to be optimized such that the image qualities of the B mode, the color mode, and the Doppler mode balance depending on, for example, the measurement condition.
To do this, the ultrasonic diagnostic apparatus is provided with a switch called IQ-balance. Using the switch, the examiner (user) can select the Doppler mode, the B mode, or the color mode to emphasize the image quality. For example, to emphasize the image quality of the Doppler mode, the number of data of the Doppler mode is increased to shorten the gap period, thereby improving the image quality of the Doppler mode. On the other hand, to emphasize the image qualities of the B mode and the color mode, the number of data of the Doppler mode is decreased, and the number of data of the B mode and the color mode is increased, thereby improving the image qualities of the B mode and the color mode.
In the ultrasonic diagnosis, various blood flows of a subject can be measured in the Doppler mode. The blood flows measured in the Doppler mode include a pulsating blood flow that temporally changes the flow velocity along with the heartbeat (to be referred to as a pulsating flow hereinafter) and a blood flow having a predetermined flow velocity (to be referred to as a steady flow hereinafter).
If the blood flow to be measured is the pulsating flow, the degradation in the Doppler waveform in the Doppler mode is noticeable. Hence, it is therefore necessary to shorten the gap period by increasing the number of data of the Doppler mode.
On the other hand, if the blood flow to be measured is the steady flow, the degradation in the Doppler waveform in the Doppler mode is relatively small even when the above-described gap period is long.
For this reason, the number of data of the B mode and the color mode (that is, the data distribution in the B mode and the color mode) can be increased.
As described above, the feature of (the degradation in) the Doppler waveform changes between the pulsating flow and the steady flow. However, examination is generally performed without changing the data distribution between the B mode, the color mode, and the Doppler mode depending on whether the blood flow to be measured is the pulsating flow or the steady flow. In addition, the examiner may determine the pulsating flow or the steady flow and change the above-described IQ-balance each time. However, this operation is cumbersome for the examiner.
Hence, there is demanded a mechanism for automatically optimizing the image quality of each operation mode when simultaneously displaying images in a plurality of operation modes including the Doppler mode as in the above-described Triplex mode.